Switch device

ABSTRACT

A manually operated switch device with small operating play and precise function for the control of electrical equipment which includes a switch housing which has stationary contacts adapted thereto, and a contact bridging element with moving contacts which is adapted to be movable. The switch is operated by means of an actuating member which is movable in the interior of the switch housing and which is capable of transferring, by a rotational motion of the actuating member, the moving contacts for engaging and disengaging with the stationary contacts, and by means of a transmission means for converting the rotational motion of the actuating member into an axial motion. Springs are adapted to cooperate with the transmission means for exerting a spring force onto said transmission means for engaging and disengaging said contacts by having at least two springs located at the opposite sides of the actuating member for exerting a symmetrical spring force on said actuating member and said transmission means.

This application claims the benefit under 35 U.S.C. §371 of prior PCTInternational Application No. PCT/FI 96/00281 which has an Internationalfiling date of May 22, 1996 which designated the United States ofAmerica, the entire contents of which are hereby incorporated byreference.

BACKGROUND OF THE INVENTION

The present invention is related to a manually operated switch devicefor the control of electrical equipment.

For switches employed in electrical equipment, the switch position orthe switch status must be secured so that an uncontrolled change of theswitch status cannot occur. An inadvertent starting of an electricalapparatus may occur due to, e.g., vibration or a strong shock whichcauses the movement of the switch into a wrong position resulting indangerous, hazardous situations, such as the unintentional starting ofequipment. Inadvertent switching-on of electric power in a circuit mayalso be hazardous during, e.g., maintenance operations. Correspondingly,unintentional toggling of a switch into the zero position, that is,switching off the current from an electric circuit may cause machinerydamage due to uncontrolled stopping of actuators. Due to such problems,reliable latching of equipment switches in their ON and OFF positions,must be secure with the help of, e.g., spring-loaded means.

Positive latching of a switch position can be implemented by means of,e.g., a cam attached to the switch operating shaft, whereby the cam isfollowed by a spring-loaded lever. The lever is provided with a guideslot suited to accommodate a guide pin fixed to the body structure ofthe switch. The loading spring of the lever is adapted about the leverand compressed between the guide pin and the meeting point of the leverwith the cam. When the switch is in its ON position or its OFF position,respectively, the spring latches the switch positively in its setposition and prevents uncontrolled rotational motion of the switchoperating shaft. As the switch operating shaft is rotated, the spring iscompressed between the guide pin and the cam tip. After the cam tip isrotated into its top dead center position, the toggling point of thedetent cam/lever system is attained and as the cam is further rotatedover its TDC position, the spring pushes the cam and the attachedoperating shaft of the switch into its opposite position.

However, such a switch construction has some drawbacks. Although thespring can latch the switch positively in a correct position at the endsof the shaft rotational travel, the operation of the switch is ratheruncontrolled in the middle of the shaft rotational travel. In the TDCposition of the detent cam/lever mechanism, the spring force is orientedparallel to the longitudinal axis of the detent cam/lever combination,thus being exerted onto the switch operating shaft and not exerting arotational force on the switch operating shaft and the guide pin.Consequently, this sector of the rotational travel forms an undeterminedposition of the switch setting, in which the switch may remain afteroperation by a careless user. The mutual friction between the switchmembers makes such a position uncontrollable and relatively easilypermits the switch to assume this intermediate position. As theintermediate position coincides with the TDC position of the detentcam/lever mechanism, the position is quite labile. Therefore, a switchleft in this intermediate position may readily toggle from thisintermediate position due to, e.g., a small shock into either limitposition. As a result, such an uncontrolled change of switch positioncan cause an inadvertent starting of equipment or switching-on of powerin an electric circuit supposed to be at zero voltage. Obviously, ahazardous situation occurs.

In addition to the discussion above, a conventional switch has thedrawback that the operating speed of the switch is dependent on theoperator action. This property degrades the electrical performancespecifications of the switch. When the switch is operated using, e.g.,too low a torque, the switching action does not take place at asufficient speed, whereby an arc will be formed between the contactsthat can destroy the switch very quickly as the energy released by thearc obviously has the greater burning effect the longer the arc ismaintained. In addition to inadvertent arcing, the switch can bewillfully misused by keeping the switch in a position that makes amarginal connection via the burning arc. Obviously, such a misusedestroys the switch very rapidly.

Disclosed in FI Pat. No. 93,502 is a switch device in which the switchbody is provided with at least one linearly movable slide member withcontacts adapted to cooperate with the stationary contacts of theswitch. To the slide member, via at least one spring-type member, isconnected, parallel with the slide member, a movable spring-arming platewhich during the motion of said plate causes the slide member tocorrespondingly move under the force exerted by said springs. While thisswitch device embodiment provides a reliable and rapid switching actionand unambiguous position indication, the structure of the contactsurfaces permits operation of this device alone at relatively lowcurrents.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a switchconstruction offering distinct and secure latching in the OFF positionand the ON position, respectively, during the operation of the switchand having blade-like contact surfaces.

It is a further object of the present invention to provide a switchconstruction in which the operating member always assumes a positionclearly indicating the status of the switch contacts and is capable ofactuating the switch contacts at a high speed independent of the manualactuating speed exerted by the operator.

It is still a further object of the present invention to provide aswitch with a minimal operating play and precise function.

The goal of the present invention is achieved by controlling the contactbridging element of the switch device by means of a symmetricaltorque-exerting mechanism.

The symmetrical torque-exerting mechanism forces the contact bridgingelement to move along its center line and the slidable actuating memberswhich control the bridging element are arranged to move in oppositedirections, thus minimizing the accumulating effect of slackness due tothe flexing and play of the members. The play in the toothed contactbetween the actuating member and the slide member can be minimized.Thus, the operation of the switch becomes precise. The actuating torqueis evenly divided between two torque-exerting mechanisms, and further,the wear on the cam tips of the release mechanisms and the slantedsurfaces of the tipped elastic fingers of the slide member are reduced.Also the wear on the tips of the slide element elastic fingers and thelimit stops on the switch cover will be reduced by virtue of thedistributed stresses. Such a reduction of stresses imposed on the limitstops of the switch cover and the tipped elastic fingers of the slidemember is particularly valuable, because these members have a smallcontact area and the tips have to keep the slide members stationaryduring the arming of the springs until the moment of tripping. Due tothe symmetrical structure, the moving contacts meet their stationarycontacts simultaneously, which is important in closing the switch to ashort-circuit load and breaking up a load current. Further, simultaneousoperation of the contacts also results in uniform wear of the contacts.The position indication will be positive and reliable as the positionindication limiters abut the limit stops of the contact bridging elementin both limit positions.

The actuating member stays on the center line, because it simultaneouslycontrols two torque-exerting mechanisms actuating with identicaltorques. This arrangement prevents lateral yielding deformation of theactuating member. When the number of the slide members is two, the loadimposed on the toothed torque-transmitting mechanism is halved. Morespace is provided for the motion of the bridging element in thedirection of the actuating member axis and for a larger contact openinggap. The actuating member can be recessed deep into the bridgingelement, since the arrangement of symmetrically exerted torque relievesthe member from lateral forces that could cause friction and therebydegrade the operating precision of the switch device. The actuatingmember shaft can have a long adjustment span, whereby the actuating knobcan be positively secured to a long shaft, thus avoiding the use ofspecial-design shafts. The paired guide slots for the slide membersmoving the bridging element can be provided with a steep pitch angle dueto the opposite direction motion of the slide members. Particularlyadvantageously, the guide slots are provided with a variable pitch angleformed into, e.g., circular arcs.

Due to the dual torque-exerting mechanism construction, the presentswitch device will function even when one of the torque-exertingmechanisms is damaged or the limit stop on the cover is worn orotherwise broken. In such a situation, the other torque-exertingmechanism has to bear a doubled mechanical load, whereby its wear rateis obviously accelerated. Nevertheless, this property allows the serviceof the switch device to be extended as necessary in cases that do notpermit immediate replacement of a damaged switch with a new device. Saidproperty also improves reliability and operating safety, because noinstantaneous damage and loss of function can occur in the switchdevice, but instead, current switching and breaking can in most cases bemade even with a partly damaged switch.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention will be examined in more detail withreference to the attached drawings, in which:

FIG. 1 is an exploded view of a switch device according to the presentinvention;

FIG. 2 is a perspective view of a group of elements of the switch deviceillustrated in FIG. 1 assembled together;

FIG. 3 is a perspective view of another group of elements of the switchdevice illustrated in FIG. 1 assembled together;

FIG. 4 is a top plan view of the toothed actuating mechanism of theswitch device illustrated in FIG. 1; and

FIG. 5 is partially sectional perspective view of the switch deviceillustrated in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, the housing of the switch device is comprised of acover 1 and a body 2. The cover 1 has fastening clips 4 which areinsertable into compatible holes of the body 2 thus fixing the cover inplace. It should be noted that while in reality the cover 1 and the body2 form a closed housing except for the entry holes of the cables, forpurposes of illustration the annexed diagrams show views with cut-outwindows to facilitate an easier description of the functions of theswitch elements.

Still referring to the exploded view of FIG. 1, the principal elementsof the switch device are shown therein. Stationary contacts 11 andquenching plates 13 are attached to the body 2 and the moving contactbridging element 20 is disposed between them so that the contacts 12 ofthe bridging element are located below the stationary contacts 11 andbetween the quenching plates. The actuating member 6 is adapted to moveinto the opening of the bridging element 20, and slide members 9supported by the guide pins 17 are provided at both sides of thebridging element. The slide members 9 have trip elements 10 which fitinto their corresponding slots 18 so that the flanges 19 of the tripelements 10 are located in the slots 18 of the slide members 9. Theslide members 9 and the trip elements 10 are also provided with a spacesuitable for accommodating torque-generating springs 8. The slidemembers, trip elements and springs together form the torque-exertingmechanism of the switch device.

In FIGS. 2 and 4 the bridging element 20 and the trip elements 10 areshown with their slide members 9. In FIG. 3 these switch device partsare shown in an exploded perspective view separate from each other. Theflange 19 of the trip element 10 forms an annular recess providing aspace for the torque-generating spring 8, and the slide members 9incorporate a space suitable for accommodating the flange 19 of the tripelement 10 and the spring 8 inserted therein. After the insertion of thespring 8 into the annular spring-accommodating space of the flange 19,the spring will be backed at the center line of its ends by the ends ofthe spring space in the flange. When the flange 19 with the spring 8 areinserted in the slide member 9, the ends of the spring-accommodatingspace coincide with the ends of the spring so that if the trip elements10 are moved relative to the slide members 9 in the axial direction ofthe spring 8, the spring 8 will be compressed by the flange 19 and theslide member. In FIGS. 2 and 3 are also shown the guides 24 of thebridging element 20 that run on longitudinal stiffeners 31 extending tothe interior of the body 2. The sliding elements 9 and the trip elements10 slide in a ready-assembled switch device on the upper surfaces of thestiffeners 31. The inner surfaces of end hooks at one end of the tripelements have position limit stops 23.

As shown in FIG. 3, the motion of the bridging element 20 of the slidemember 9 is guided by a pair of slanted slots 25. In a ready-assembledswitch device, the guide pins 17 of the bridging element are adapted torun along these slots 25, whereby the longitudinal motion of the slidemember forces the bridging element 20 to perform a vertical motion dueto the oppositely located pair of guide slots with the guides 24 actingso as to support the motion. The motion of the slide member 9 isaccomplished by means of the trip element 10, and the trip element 10 inturn is moved by means of a mechanism comprising the teeth 7 of theactuating member and the mating teething 22 formed on the side surfacesof the trip element 10. In the illustrated embodiment, the actuatingmember 6 has two sets of three teeth on the opposite sides of theactuating member 6 which are designed so as to mate with the teeth 22 ofthe opposedly located trip elements.

Referring to FIG. 5, the switch cover 1 has backing surfaces 26 of thecover 1 adapted to rest against the stop surfaces 21 of the tippedelastic fingers 16 of the slide member 9 which halt the motion of theslide members during the arming of the springs 8. In the diagram of FIG.5 are also shown cable terminal clamps 27, whose number in the switchdevice embodiment illustrated therein is three on both sides of theswitch.

The switch embodiment described above is operated as follows. The armingof the torque-generating springs 8 and the motions of the differentswitch elements occur in an identical fashion when the switch isactuated into its ON and OFF positions, obviously using, however,reversed actuating directions. Because of the symmetrical operation ofthe switch device, the corresponding motions in both groups of matingparts take place on both sides of the actuating member 6. When thecontrol knob 3 is resting in position 0 or 1, one of the stop surfaces21 of the tipped elastic fingers 16 rests against the backing surface 26of the cover. As the control knob 3 is rotated, the teeth 7 of theactuating member 6 transmit the rotational motion to the teeth 22 of thetrip elements 10. Since the slide members 9 are still stationary, thetrip elements 10 can compress the springs 8 located inside the slidemembers 9. Simultaneously, the trip element tips 14 move along the uppersurfaces of the tipped elastic fingers 16 until meeting the slantedsurfaces 28 of the fingers behind the stop surfaces 21. When themovement of the control knob 3 and the trip elements 10 is continued,the trip tips 14 release the tipped elastic fingers 16 from theirlocking to the cover thereby tripping the slide members 9. At thismoment, the control knob 3 has moved to approx. a 60° angle of rotation.At the tripping of the slide members 9, they are moved at a high speed,horizontally pushed by the compressed springs 8 thereby actuating thebridging element 20 to move vertically under the support by the guidepins 17 of the slide member 9 running in the slanted slots 25. Duringthis motion, the moving contacts 12 attached to the bridging element 20are also moved, whereby the load current is switched on or off dependingon the direction of the motion of the bridging element. Simultaneously,the stop surfaces 21 of the tipped elastic fingers 16 at the oppositesides are passed behind the backing surfaces of the cover 1, whereby thecontrol knob locks to indicate the selected switch position. In eitherswitch position the torque-generating springs 8 remain only slightlyprecompressed in the interior space of the slide members 9 and tripelements 10 with their ends brought to the same plane, whereby theswitch will be relieved from extraneous static stresses.

In the event of inadvertent welding-together of the contacts 11, 12 forany reason, their force-controlled separation can be attempted. In thepresent switch embodiment such a forced control is implemented by meansof force-control tips 15 provided on the trip elements 10. Theforce-control tips 15 move in a slot formed below the spring-enclosingrecessed space of the slide member 9 and the length of the slot isdimensioned so that the force-control tips 15 do not normally hit theends 30 of the slot. In the case the contacts 11, 12 are not separatedunder the force imposed by the springs 8, the force-control tips 15 canmeet the ends of the slot, whereby contact separation can be attemptedby imposing a higher manual force via the control knob 3 on the bridgingelement. Should the separation of the contacts fail, the control knobremains by an angle of approx. 25°, short of the switch-open positionand returns to the switch-closed position when the control knob 3 isreleased. Should the contacts separate only incompletely, the positionlimit stops 23 of the trip elements 10 meet the stops 29 of the bridgingelement 20 and the control knob remains by an angle of approx. 20°,short of the switch-open position and returns into the switch-closedposition when the control knob 3 is released. The angles of the controlknob rotation cited above are obviously exemplary and dependent on thedimensions and motion timing of the switch.

In addition to the preferred embodiment of the present inventiondescribed above, the present invention can be implemented in a pluralityof alternative manners.

Obviously, the appearance and design of the different elements of theswitch device may be varied widely. The torque-generating springs may beselected from coiled springs, leaf springs and other elements capable ofexerting a sufficient spring force. While the number of spring elementsmust be at least two, parallel spring elements can be used if desired sothat the springs together form a single spring element in thetorque-exerting mechanism. The shape and number of guiding slotsactuating the contact bridging element of the slide member can bevaried, and advantageously, the slots with a variable pitch angle can beutilized to generate a high torque, whereby a suitable design of theguide slot shape can assist the handling of the control knob. The guideslots may alternatively be designed into the contact bridging element,whereby the slide members must be provided with compatible pins or otherguide elements.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art wereintended to be included within the scope of the following claims.

I claim:
 1. A switch device comprisinga switch housing, stationarycontacts disposed within the switch housing, a contact bridging elementwith moving contacts which is movable in the interior of the switchhousing, an actuating member which is movable in the interior of theswitch housing for transferring by a rotational motion of the actuatingmember, the moving contacts for engagement and disengagement with thestationary contacts, a transmission means for converting the rotationalmotion of the actuating member into an axial motion, and first springscooperating with said transmission means for exerting a spring force tosaid transmission means for engaging and disengaging said stationary andmoving contacts, wherein at least two of said first springs are employedand located at opposing sides of the actuating member for exerting asymmetrical spring force on said actuating member and said transmissionmeans.
 2. The switch device as defined in claim 1, containing two ofsaid first springs.
 3. The switch device as defined in claim 2, whereinsaid transmission means comprises two identical torque-exertingmechanisms containing actuating springs, whereby the torque-exertingmechanisms are symmetrically disposed on opposite sides of saidactuating member.
 4. The switch device as defined in claim 1, whereinsaid transmission means comprises two identical torque-exertingmechanisms containing actuating springs, whereby the torque-exertingmechanisms are symmetrically disposed on opposite sides of saidactuating member.
 5. The switch device as defined in claim 4, whereineach of said torque-exerting mechanisms moves in a directionperpendicular to the plane of said contact bridging element each of saidtorque-exerting mechanisms including slide members containing slantedslots and said contact bridging element containing guide pins whichmovably fit in said slots, whereby the motion of said bridging elementis accomplished by the motion of said slide members in cooperation withsaid slots and the guide pins.
 6. The switch device as defined in claim5, wherein said slide members contain tipped elastic fingers and saidcover contains backing surfaces which define the path of the tippedelastic fingers so as to prevent uncontrolled motion of the slidemembers, each of said torque-exerting mechanisms further containing atrip element which moves relative to said slide members and has a triptip which moves with one of said tipped elastic fingers so that themovement of the trip tip can release the one of the tipped elasticfingers from being locked by one of said backing surfaces.
 7. The switchdevice as defined in claim 6, wherein each of said trip elements has arecessed space for accommodating a corresponding one the first springsand each of said slide members contains a recessed space foraccommodating a portion of a corresponding one of said trip elementsthat houses said springs corresponding one of said first in a fashionthat permits moving said corresponding one of said trip elementsrelative to each of said slide members in order to arm said one of saidfirst springs spring.
 8. The switch device as defined in claim 7,wherein each of said trip elements has a force-control tip and each ofsaid slide members has two backing surfaces which coincide with themovement of the force-control tips so that the distance between theforce-control tips and the backing surfaces is larger than the distancebetween the armed and tripped positions of said trip elements.